1. Field of Invention
This invention relates to steerable catheters. More particularly, this invention relates to an improved catheter tip for a steerable catheter which when bent consistently deflects within a single plane without undesired twisting.
2. Prior Art
Catheters of various types have been utilized for medical procedures for many years. For example, they have been used to convey an electric stimulus to a selected location within the human body or to monitor or make measurements for diagnostic purposes of activities within the human body. Such catheters examine, diagnose and treat areas which are otherwise inaccessible without invasive procedures. In use, the catheter is first inserted into a major vein or artery or other body lumen which is near the body surface. The catheter is then guided to the area for examination, diagnosis or treatment by manipulating the catheter through the body lumen. As the utilization of catheters in remote and difficult to reach locations within the body has increased, it has become more important to control precisely the movement of the tip of the catheter within the body lumen.
Control of the movement of catheters is difficult because of their construction. The body of conventional catheters is long and tubular. To provide sufficient control over the movement of the catheter, it is necessary that these tubular catheters be made somewhat rigid. However, these catheters must also be flexible enough to navigate through the body lumen to arrive at the desired location within the body where the desired medical procedures will occur without harming the body lumen.
One of the early methods used to control the movement of catheters within a body lumen was by preshaping catheter tips. This construction had advantages for certain limited medical procedures, but because the configuration of the bend could not be changed after insertion and because of the difficulty in orienting the bend in the desired direction as a result of the torsional flexibility of the catheter, new improved catheters were necessary.
Short and rigid controllable tip devices have also been used for special procedures where the degree of bending of the tip could be controlled from the handle. However, these devices are not satisfactory for vascular purposes where the catheter must be long, slender and flexible throughout its entire length.
To increase the ability to move and navigate within a body, longer, flexible catheters containing steerable, deflectable tips have been designed. Because the deflectable tips of these flexible catheters are readily bendable, they can be used for a number of medical procedures which require precise control over the orientation of the catheter tip. With these devices the bending of the steerable tip is achieved by increasing or decreasing the axial compressive force on one side of the steerable tip by applying tension to a pull wire which runs the entire length of the catheter. By increasing the compressive force to one side of the tip, it is bent.
To control precisely the movement of these steerable catheters, control handles have been attached at the proximal end of the catheter body. For example, U.S. Pat. No. 4,586,923 describes certain devices useful for controlling the movement of steerable catheters. See also U.S. Pat. Nos. 5,254,088, 5,195,968, 5,186,004, 5,125,896, 5,190,050 and 4,960,134.
While use of a pull wire to deflect the tip of a steerable catheter is effective in bending the tip, the lateral movement of the catheter tips of existing devices as they are being bent is not always consistent. Further, axial rotation of the catheter tip of existing devices during the bending of the catheter tip frequently occurs resulting in imprecise and inexact location of the catheter tip. Thus, improved catheters are necessary to control the direction of bending of the tip of the catheter and restrict its axial rotation as it is being bent by the pull wire. One method to limit the lateral movement of the tip portion of the catheter while it is being bent by a pull wire is by the introduction into the catheter tip of a generally flat supporting wire. See, for example, U.S. Pat. No. 5,190,050 which discloses the use of three flat planer shims juxtaposed in sandwiched relation and mounted within the tip and body of a catheter. The use of a single flat supporting wire is also disclosed in U.S. Pat. No. 5,125,896. See also U.S. Pat. No. 4,920,980.
While this use of a flat supporting wire, either singly or in combination, does assist in maintaining the catheter tip in a single plane while it is being bent, problems relating to the torquing or twisting of the catheter tip as it is being bent still occur. Thus, new designs for catheter tips are important to provide enhanced lateral stiffness to the catheter tip during the bending process while still retaining the relatively soft feel of the tip of existing catheter.
Accordingly, it is an object of this invention to disclose an improved steerable catheter tip.
Another object of this invention is to disclose a steerable catheter tip with improved structure that permits deflection of the catheter tip only in a single plane.
Another object of this invention is to disclose a steerable catheter tip where the structure of the lumen of the catheter tip is designed to receive a supporting flat wire which will also provide additional lateral stiffness to the catheter tip.
It is a still further object of this invention to disclose an improved steerable catheter tip whose structure will permit limited axial rotation of the catheter tip while it is being bent.
These and other objects are obtained by the design of the steerable catheter of the instant invention.